Conventionally, pilots use weather radar to detect and avoid hazardous weather. Conventional radar systems may produce the desired results only in a limited environment. Typically, airborne threshold systems use thresholds for wet precipitation derived from ground-based weather radar thresholds which were generated from convective weather detections. Such thresholds have been set in accordance with reflectivity data which is applicable to typical convective weather systems. It has been observed that for airborne applications ground clutter causes differences in reflectivity which may cause inaccurate weather indications. A feature of conventional radar systems is the ability to suppress display of returns from the ground in favor of returns from weather. These ground clutter suppression systems may have limited effectiveness with certain local geographical conditions, such as in the presence of cities, especially cities near bodies of water, and with tall objects, such as towers beyond the horizon. Such ground clutter may erroneously be presented as a weather target. Conventionally, weather radar ground clutter suppression systems may rely on different return signals resulting from radar beam sweeps occurring at different beam elevations. Even so, many geographical phenomena may not be suppressed using present ground clutter suppression systems.
Conventionally, radar thresholds map radar return strength to a display with color representing rain rate or alternatively a weather threat assessment level. The threat level has been previously described as primarily a function of radar reflectivity and a weaker function of temperature, altitude, and latitude. However, because of various geographical phenomena, the conventional mapping, while useful, does not completely allow successful operation of aircraft in difficult geographic situations. The higher reflectivity of these geographic phenomena produces erroneous detection of significant convective weather systems during flight. Further, because of the ability of aircraft flying over such geographical phenomena to circumnavigate storm systems, when believed to be present, it would therefore be desirable to provide an airborne radar system which has the ability to more accurately detect and report the existence and/or characteristics of storms when operating in various geographically diverse environments.
It may be possible for a pilot operating a radar manually to be able to compensate for the differences in geographical phenomena as each pilot becomes familiar with the environment. However, knowledge by the pilot must be acquired, and further, an increase in pilot workload is also necessitated. Therefore, there is a need for an automated system of adjusting radar thresholds based on the presence of a variety of geographical phenomena.
In addition, ground clutter reflectivity can vary by time of day and time of year, in various geographical regions. For example, dew forming on grass increases ground reflectivity. Ground reflectivity also may vary depending on whether forests are leaf covered or bare or whether fields are filled or fully vegetated. Similarly, snow covered landscapes reflect differently than green grasslands. Thus, it may be desirable to identify ground clutter in accordance with temporal information.
In addition, weather characteristics can change according to seasonal and time-of-day variations. For example, certain radar reflectivities occurring during the monsoon season may indicate hazardous weather while those same radar reflectivities would indicate non-hazardous weather during another season. Similarly, weather radar returns at a certain time-of-day are more likely to indicate the presence of hazardous weather (e.g., afternoon) while those same returns are less likely to indicate the presence of a hazard at another time-of-day (e.g., early morning). Accordingly, it would be desirable to provide a radar system which can compensate radar detection in accordance with both temporal and spatial information.
Accordingly, there is a need to adjust weather radar detection and ground clutter suppression schemes based upon a specific geographic location, time-of-day, and/or season (time-of-year). There is further a need to adjust weather radar systems by adjusting display thresholds, tilt angle, and/or system gain. Yet further, there is a need for a weather radar system that automatically adjusts to location time-of-day, and/or time-of-year. Yet further still, there is a need to adjust weather radar systems by adjusting thresholds and parameters based on known ground clutter locations.
It would be desirable to provide a system and/or method that provides one or more of these or other advantageous features. Other features and advantages will be made apparent from the present specification. The teachings disclosed extend to those embodiments which fall within the scope of the appended claims, regardless of whether they accomplish one or more of the aforementioned needs.